Inhibition of prolyl 4-hydroxylase in vitro and in vivo by members of a novel series of phenanthrolinones

Abstract

Examples of a novel series of phenanthrolinones are shown to be potent competitive inhibitors of avian prolyl 4-hydroxylase, and of collagen hydroxylation, in embryonic chick tendon cells and human foreskin fibroblasts in vitro and in the oestradiol-stimulated rat uterus in vivo. Two compounds, Compound 1 (1,4-dihydrophenanthrolin-4-one-3-carboxylic acid) and Compound 5 [8-(N-butyl-N-ethylcarbamoyl)-1,4-dihydrophenathrolin-4-one-3-carboxylic acid], with comparable potencies in vivo, were chosen to investigate the effect of the inhibition of the hydroxylation of newly synthesized uterine collagen on the turnover of this protein in vivo. Inhibition of hydroxylation by more than 50% for approx. 8h following single oral doses of the compounds was associated with significant losses of radiolabelled proline and 4-hydroxyproline from collagen during this period. Progressive hydroxylation of collagen over 48h, as the inhibitory action of the compounds declined, was accompanied by a decreased loss of radiolabel from the uterine collagen. Earlier reports indicated that underhydroxylated collagen, accumulating within the endoplasmic reticulum in cells where prolyl 4-hydroxylase is inactivated, is slowly degraded, but is then rapidly hydroxylated and secreted when the activity of prolyl 4-hydroxylase is restored. Taken with the present results, this suggests that the potential use of inhibitors of prolyl 4-hydroxylase to control excessive collagen deposition in pathological fibrosis may be limited by the need to maintain continuous inhibition of collagen hydroxylation so as to facilitate intracellular degradation of the accumulated protein.

Mitochondrial localization of TIGAR under hypoxia stimulates HK2 and lowers ROS and cell death

“…1 B and C). Treatment of cells with DPCA or DMOG, small molecules that lead to the stabilization of HIF1α (24,25), also promoted the relocalization of TIGAR to mitochondria ( Fig. 1 D and E)-although it should be noted that these drugs generally inhibit prolyl 4-hydroxylases and will therefore have additional, HIF1α-independent effects.…”

Inhibition of Histone Demethylases by 4‐Carboxy‐2,2′‐Bipyridyl Compounds

“…It is possible that potency of the bipyridyl compounds can be increased further by using the crystal structure of 13a in complex with JMJD2A, including by further derivatisation of the 4-carboxylate to occupy the N ε -methyllysine side chain binding groove. Notably, bipyridyl compounds have been found to inhibit both the collagen prolyl-4-hydroxylases [15,21] and the hypoxia inducible factor prolyl-4-hydroxylases, [16] suggesting that these compounds might be relatively generic inhibitors of 2OG oxygenases. Our work could thus enable the rational structurebased functionalisation of the bipyridyl template to enable the production of inhibitors with different selectivities for use in biological research and medicinal applications.…”

How oxygen makes its presence felt: Figure 1.

“…As suggested earlier, pharmacological blockade of HIF hydroxylation might augment the cellular response to hypoxia and thereby promote cell survival (Bruick and McKnight 2001a;Ivan et al 2001). Studies of the collagen prolyl hydroxylases, which are required for collagen maturation, first established the feasibility of inhibiting this class of enzymes with small molecule iron antagonists or 2-oxoglutarate antagonists (Majamaa et al 1984;Tschank et al 1987;Gunzler et al 1988;Baader et al 1994;Franklin et al 2001). A number of these compounds, including FG0041, also inhibit HIF hydroxylation by Egl-9 (Epstein et al 2001;Jaakkola et al 2001;Ivan et al 2002).…”